More specifically, this invention applies to the manufacture of sanitary underwear such as baby nappies, sanitary towels or the like.
As is known, nappies comprise an absorbent core or pad which is normally enclosed between a permeable inner layer of non-woven fabric and an impermeable outer layer of polyethylene.
Absorbent pads of known type comprise an absorbent core made of an absorbent material, such as, for example, granules of superabsorbent polymer material (SAP) inside a mixture of containment cellulose pulp (fluff) and absorbent material binder, sandwiched between two layers of non-woven fabric.
In particular, core forming units known in the prior art comprise a station for feeding the fibrous material, or fluff, and a station for supplying the superabsorbent polymer material, the two stations being mounted in parallel and combined at a forming duct or chamber.
More specifically, prior art units comprise a mill for crushing the fibrous material, provided with one or more inlets through which the fibrous material in the form of a web or chain of fibres is fed in, and a crushing rotor in which the material is broken up as much as possible into individual fibres which are subsequently allowed to drop through an outfeed opening.
Downstream of the outfeed opening there is a forming duct which is generally provided with nozzles that deliver granules of superabsorbent polymer material which are scattered into the duct and embedded in the fluff fibres.
Disadvantageously, the scattering of the particles of superabsorbent polymer material inside the duct is often of low quality, in particular with reference to products of the latest generation, where the quantity of superabsorbent polymer material tends more and more to exceed that of the other absorbent material.